refactor(timeline): drop the canvas outer border (REQ-001)

The page is already bg-canvas, so the frame's border was the only thing
making it visible; per review it reads cleaner without it. Keep the padded
bg-canvas surface; the timeline sits on the page without a frame line.

Refs #833
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

.specify/rtm.md

@@ -123,7 +123,7 @@
 | REQ-015 | absent/empty/non-UUID originPersonId → redirect /zeitstrahl (CWE-601) | #781 | timeline-curator-forms | `frontend/src/lib/timeline/eventFormServer.ts#resolveNavTarget` | `new/page.server.spec.ts#defaults to /zeitstrahl when originPersonId is not a valid UUID`, `#redirects to /persons/{id} when originPersonId is a valid UUID` | Done |
 | REQ-016 | title/description/chip labels via default `{...}` escaping, never `{@html}` (CWE-79) | #781 | timeline-curator-forms | `frontend/src/lib/timeline/EventForm.svelte` | code review + `grep -r '@html' frontend/src/lib/timeline/` → zero | Done |
 | REQ-017 | labelled pickers, visible empty states, ≥44px chip remove targets | #781 | timeline-curator-forms | `frontend/src/lib/person/PersonMultiSelect.svelte`, `document/DocumentMultiSelect.svelte`, `EventForm.svelte` | `PersonMultiSelect.svelte.spec.ts`, `DocumentMultiSelect.svelte.spec.ts` (green post-44px fix), `EventForm.svelte.spec.ts#preselects a person when initialPersons is provided` | Done |
-| REQ-001 | `/zeitstrahl` wraps the timeline in a `.tl-canvas` frame (border, rounded, bg-canvas, semantic tokens) | #833 | zeitstrahl-visual-fidelity | `frontend/src/routes/zeitstrahl/+page.svelte` | `routes/zeitstrahl/page.svelte.spec.ts#wraps the timeline in a bordered, rounded canvas frame` | Done |
+| REQ-001 | `/zeitstrahl` wraps the timeline in a `.tl-canvas` surface (rounded, bg-canvas, padding; outer border dropped in review — page is already bg-canvas) | #833 | zeitstrahl-visual-fidelity | `frontend/src/routes/zeitstrahl/+page.svelte` | `routes/zeitstrahl/page.svelte.spec.ts#wraps the timeline in a padded canvas surface, without an outer border` | Done |
 | REQ-002 | meta sub-line: range + letter count + event count (years + undated) + "Gruppierung: Datum"; range/line omitted when empty | #833 | zeitstrahl-visual-fidelity | `frontend/src/lib/timeline/timelineMeta.ts`, `frontend/src/routes/zeitstrahl/+page.svelte` | `timelineMeta.spec.ts` (4 cases), `routes/zeitstrahl/page.svelte.spec.ts#renders the meta sub-line`, `#omits the range segment`, `#omits the entire sub-line` | Done |
 | REQ-003 | year badge centered on axis ≥1024px, left spine <1024px; sticky top:4rem preserved | #833 | zeitstrahl-visual-fidelity | `frontend/src/lib/timeline/YearBand.svelte` | `YearBand.svelte.spec.ts#centers the year badge on the axis at desktop`, `#left-aligns the year badge at phone width`, `#keeps the sticky year heading at top:4rem` | Done |
 | REQ-004 | year badge node marker on the spine, never overlapping the badge text (desktop + phone) | #833 | zeitstrahl-visual-fidelity | `frontend/src/lib/timeline/YearBand.svelte` | `YearBand.svelte.spec.ts#renders a year-badge node marker that clears the badge text on phone` | Done |

frontend/src/routes/zeitstrahl/+page.svelte

@@ -30,9 +30,10 @@ const metaLine = $derived.by(() => {
 </svelte:head>
 
 <div class="mx-auto max-w-5xl px-4 py-8">
-	<!-- The .tl-canvas sheet: a framed surface the timeline reads as a finished
-	     life-thread rather than bare page chrome (REQ-001). -->
-	<div data-testid="timeline-canvas" class="rounded-[10px] border border-line bg-canvas p-6">
+	<!-- The .tl-canvas sheet: a padded canvas surface for the timeline. The outer
+	     border is intentionally omitted (the page is already bg-canvas), per the
+	     review of REQ-001 — the sheet reads through its padding, not a frame line. -->
+	<div data-testid="timeline-canvas" class="rounded-[10px] bg-canvas p-6">
 		<h1 class="font-serif text-2xl font-bold text-brand-navy">{m.timeline_heading()}</h1>
 		{#if hasContent}
 			<p data-testid="timeline-meta" class="mt-1 mb-6 font-sans text-xs text-ink-3">{metaLine}</p>

frontend/src/routes/zeitstrahl/page.svelte.spec.ts

@@ -29,15 +29,16 @@ const pageData = (timeline: ReturnType<typeof makeTimelineDTO>) => ({
 });
 
 describe('/zeitstrahl page', () => {
-	it('wraps the timeline in a bordered, rounded canvas frame (REQ-001)', () => {
+	it('wraps the timeline in a padded canvas surface, without an outer border (REQ-001)', () => {
 		render(Page, {
 			data: pageData(makeTimelineDTO({ years: [makeYear(1909, [makeEntry()])] }))
 		});
 		const canvas = document.querySelector('[data-testid="timeline-canvas"]');
 		expect(canvas).not.toBeNull();
 		expect(canvas?.classList.contains('bg-canvas')).toBe(true);
-		expect(canvas?.classList.contains('border')).toBe(true);
-		// the timeline renders inside the frame
+		// The outer border was dropped in review (the page is already bg-canvas).
+		expect(canvas?.classList.contains('border')).toBe(false);
+		// the timeline renders inside the surface
 		expect(canvas?.querySelector('ol')).not.toBeNull();
 	});